1. Field of the Invention
This invention relates to an apparatus and method of embedding data into a signal or updating data that are already embedded into a signal, and more particularly to an apparatus and method of embedding specific data (electronic watermark) into a plurality of audio signals, or updating specific data that have been embedded into a signal using a minimum amount of operations.
2. Description of the Related Art
In recent years, with the spread of personal computers, CD-R drives, and the Internet, and due to inexpensive high-capacity recording media such as hard disc drives and the like, pirated versions of music CDs or compressed files that have been illegally compressed on the Internet are being distributed improperly in large amounts. Improper use of these contents violates the rights of those holding the copyrights, and has become a major problem in today""s society.
In the midst of this kind of situation, recently much attention has been placed on electronic watermarking technology as a new technology for copyright protection. Electronic watermarking technology, for example, is already being used in DVD audio discs and players. Electronic watermarking is a technique of embedding some digital data into an audio signal by adding minute noise or distortion that is not noticeable by human hearing. Moreover, since this electronic watermark is a very minute signal, humans cannot hear the embedded electronic watermark when a player for the music contents reproduces that audio signal.
Next, how copyrights are protected by using an electronic watermark will be explained in general. First, the disk manufacturer or copyright holder embeds digital data into the audio signal using a predetermined format, indicating xe2x80x98Copy One Generation xe2x80x99. In the case of using technology that takes advantage of electronic watermarking as copyright protection technology for music contents, in many systems, copyright protection is performed effectively by embedding an electronic watermark in the signal output from every channel that contains music contents.
The case of embedding an electronic watermark will be explained in more detail using FIG. 19 and FIG. 20. FIG. 19 is a schematic drawing of a data-addition apparatus 1901 that is used when embedding an electronic watermark into a specific audio signal. FIG. 20 is a schematic drawing of a data-update apparatus 2011 that detects and updates an electronic watermark that was embedded by the data-addition apparatus 1901. The audio signal is a signal such as a music or voice signal that stimulates the sense of hearing when reproduced.
For example, when reproducing music contents that perform stereo output, there are two output channels for the audio signal so two kinds of audio signals are output. In this case, by equipping the data-addition apparatus 1901 with a first signal-addition means 1904 that embeds an electronic watermark into the audio signal (L channel) 1902 and outputs an audio signal 1903 embedded with an electronic watermark, and a second signal-addition means 1907 that embeds an electronic watermark into the audio signal (R channel) 1905 and outputs an audio signal 1906 embedded with an electronic watermark, electronic watermarks are embedded into two kinds of audio signals. The audio signals 1903, 1906 embedded with electronic watermarks are then recorded on a medium such as a CD or DVD as audio contents embedded with electronic watermarks, or they are recorded using a recording apparatus as data for distribution. The first and second signal-addition means 1904, 1907 use specific key data as required when embedding electronic watermarks.
Here, the data embedded as an electronic watermark are, for example, data for restricting the number of times the audio contents whose copyright is to be protected can be copied, such as xe2x80x98Copy One Generationxe2x80x99, xe2x80x98No More Copiesxe2x80x99 or xe2x80x98Copy Freelyxe2x80x99; or it can be data such as an ID that is unique for all audio contents such as the IRSC (International Standard Recording Code).
The audio signal that is embedded with an electronic watermark is supplied to the consumer as a DVD audio disc sold at a shop, or music contents that are distributed via the Internet, etc. The consumer purchases the disk or distributed contents in which the electronic watermark is embedded.
An example of handling the electronic watermark when copying contents will be explained using FIG. 20 as a reference. To copy the contents recorded on the disk, the consumer can connect a reproduction apparatus 2001 with a recording apparatus 2002, and record the contents reproduced by the reproduction apparatus 2001 with the recording apparatus 2002. In this way, for example, the music on a DVD audio disc is copied onto a recording medium 2010, however, in the recording apparatus 2002, a data-update apparatus 2011 detects the electronic watermark that is embedded on the disk and determines whether the music to be copied are allowed to be copied.
In the case that a xe2x80x98Copy One Generationxe2x80x99 electronic watermark is embedded in the music to be copied, the electronic watermark is updated to xe2x80x98No More Copiesxe2x80x99 and recorded. Updating the electronic watermark will be explained in detail.
First, the audio signal that is input to the recording apparatus 2002 is a two-channel stereo signal having a L-channel (audio signal 1903 that is embedded with an electronic watermark) and a R-channel (audio signal 1906 that is embedded with an electronic watermark). The L-channel audio signal 1903 that is input to the recording apparatus 2002 is input to a first detection means 2003, and the first detection means 2003 detects the electronic watermark that is embedded in the L-channel audio signal 1903. A first judgment means 2004 determines whether or not the electronic watermark that is detected and input by the first detection means 2003 needs to be updated.
In other words, when the embedded electronic watermark is xe2x80x98Copy One Generationxe2x80x99, and the recording apparatus 2002 is trying to record music onto a recording medium 2010, the first judgment means 2004 sends an instruction to a first watermark-generation means 2005 to update the electronic watermark. The L-channel audio signal 2001 is then input to the first watermark-generation means 2005, and based on this audio signal, the first watermark-generation means 2005 generates an electronic watermark that cannot be heard by human hearing and which indicates xe2x80x98No More Copiesxe2x80x99.
The update watermark that is generated by the first watermark-generation means 2005 is added to the L-channel audio signal 1903 and then input to the recording means 2009. Likewise, in the case of the R-channel audio signal 1906, an update watermark signal for channel-R is generated by a second detection means 2006, second judgment means 2007 and second watermark-generation means 2008, and then it is added to the R-channel audio signal 1906 and input to the recording means 2009.
The recording means 2009 records the audio signals for each channel, whose electronic watermarks have been updated, onto the recording medium 2010.
Generally, the copy-control data for music usually does not differ between channels, so in the prior recording apparatus shown in FIG. 20, the second detection means 2006 and second judgment means 2007 can be omitted, and a switch that selects the channel can be located prior to the first judgment means to detect the audio signal for either the L-channel or R-channel and determine whether or not it must be updated. However, in the prior recording apparatus, in order to update the electronic watermark for both channels, the first watermark-generation means 2005 and second watermark-generation means 2008 are necessary.
Therefore, in the process above, when trying to use the reproduction apparatus and recording apparatus to copy the copied music again, later generation copying, for example second-generation or third-generation copying is not possible. With this process, it is possible to prevent unlimited copying of music and to protect the copyright of the music.
However, in the case of embedding an electronic watermark in each audio signal of two-channel contents for example, the amount of operations required is double that required for the case of only one channel. Naturally, in the case of embedding an electronic watermark in a maximum six-channel audio signal as in the case of DVD-Audio, six times the amount of operations is required, and as the amount of required operations increases, a problem exists in that the production cost, such as for the data-addition apparatus, becomes high due to the increased amount of memory and operation circuits.
Also, it is necessary for the data-update apparatus that updates the electronic watermark to be able to detect the electronic watermark and remove the electronic watermark when necessary. Here, it is possible for electronic watermarks that are embedded separately in multi-channel audio signals to have different waveforms even though the data of the electronic watermarks may be the same. This occurs when using a method of generating the electronic watermarks to be embedded separately based on the audio signals in which the electronic watermarks are to be embedded. In this case, it is necessary for the data-detection apparatus, data-removal apparatus and data-update apparatus to perform operations for detecting (extracting) the respective electronic watermarks for each audio signal, so several times the amount of operations is required than when embedding the electronic watermarks. As a result, a problem exists in that the production costs, such as for the data-detection apparatus, data-removal apparatus and data-update apparatus, increase due to the increase in the amount of memory and operation circuits that accompany the increase in the amount of required operations.
Also, when embedding electronic watermarks for the purpose of protecting the copyright of a music, generally the same electronic watermark data are embedded repeatedly in the audio signals of that music. This is done in order to prevent improperly copying just a part of the music.
Conventionally, to update electronic watermarks that were repeatedly embedded in the music, the data-update apparatus detected watermarks at each pre-determined watermark-detection interval of time and determined whether or not it was necessary to update the watermark based on the detected original data, and then updated the electronic watermark. In the case of an electronic watermark that uses a spectrum spread system, for example, there is an update method that writes over the electronic watermark using a different key than was used when embedding the original watermark.
In this case, as shown in FIG. 21, it was necessary for the prior data-update apparatus and recording apparatus to cover the entire music to detect the watermark when updating the electronic watermark of music and then to embed a different watermark. When a recording apparatus, or in other words, typical consumer-use recorder performs this, a problem existed in that recording took an extremely long time because the watermarks for the entire music is detected then updated.
Being proposed based on the problems described above, it is the object of this invention to provide a data-addition apparatus, data-detection apparatus, data-removal apparatus, data-update apparatus and reproduction apparatus that makes strict copyright protection possible, as well as makes it possible to greatly reduce the amount of operations required for adding, detecting, removing or updating data (electronic watermarks) in a plurality of signals.
This invention relates to a data-update apparatus that detects electronic watermarks that are embedded in input audio signals and updates the electronic watermarks when necessary, a reproduction apparatus that reproduces the audio signals including the electronic watermarks, and a data-addition apparatus, data-detection apparatus and data-removal apparatus that add, detect and remove electronic watermarks, respectively.
First, the data-update apparatus of this comprises: a channel-selection means that selects one or more channels of an input signal having a plurality of channels and outputs the channel signal corresponding to that channel; a detection means that detects an electronic watermark (data) that is embedded in the channel signal that corresponds to the channel selected by the channel-selection means; a judgment means, to which the data detected by the detection means are input, and that determines whether or not to update the electronic watermark; an update-signal-generation means that outputs an update signal for updating the detected data; and a channel-selection-addition means that adds the update signal to the selected channel.
The detection means can detect data embedded in the input signal only once, or can detect data embedded in the input signal twice, or can continue to detect data embedded in the input signal until the detection results indicate that updating the data is necessary.
Furthermore, it is also possible to have a channel-control means that specifies the channel to be selected by the channel-selection means and channel-selection-addition means.
Also, the channel-selection means can switch and select among two or more channels at specified intervals of time.
Also, the detection time of the detection means for detecting data included in the input signal is a specified time unit multiplied by the number of channels.
It is possible for the channel-control means to compare the amplitude level of the signal for each channel included in the input signal, and select the channel having the maximum amplitude level.
Moreover, the channel-control means may specify the channel based on a record of channels already selected.
Furthermore, the channel-selection-addition means may also add the update signal to channels that were not selected by the channel-selection means.
Also, comprising a first additions means that adds the signals of the channels of the input signal, and a second addition means that adds the update signal from the update-signal-generation means to the signals corresponding to the channels added by the first additions means, the update-signal-generation means may also output an update signal based on the signals added by the first addition means. Furthermore, the second addition means may add update signals to the input signals of channels other than the channels to which an update signal was added by the first addition means.
Also, channel data that specify the channels to be selected can be input to the channel-selection means, and the channel-selection means can output a channel signal based on that channel data, or it is possible to further have a recording means that correlates and records the input signals and channel data selected by the channel-selection means.
The reproduction apparatus of this invention comprises: a reproduction means that reproduces input signals in which data have been embedded, and outputs those signals as output signals; a channel-selection means, to which the output signals are input, and that selects one or more channels and together with outputting the channel signals, outputs the selected channels as channel data; a detection means that detects and output data that are embedded in the channel signals; and a transmission means that sends the channel data output by the channel-selection means and the data detected by the detection means to a specified terminal.
Moreover, the reproduction apparatus of this invention comprises: a reproduction means that reproduces an input signal having a plurality of channels; and channel-selection means that selects from the input signal and channel data that indicate whether or not the data in the input signal have been updated, channels for which the data have not been updated and outputs those channel signals; an update-signal-generation means that detects data that are embedded in the channel signal and outputs an update signal that updates the data; and a channel-selection-addition means that adds the update signal to the output signal from the reproduction means.
Furthermore, the data-addition apparatus of this invention is presumed to add a specified addition signal to each of the audio signals. Here, a first operation means outputs an addition-target signal that includes all of the plurality of input audio signals, and a separation signal that includes at least two audio signals of the plurality of audio signals; and the signal-addition means adds the specified addition signal to the addition-target signal and outputs the result as an addition-completed signal. A second operation means separates the plurality of audio signals, to which the specified addition signal was added, based on the addition-completed signal and the separation signal.
Also, the data-detection apparatus of this invention is presumed to detect the addition signal from a plurality of audio signals to which the addition signal was added. Here, a third operation means outputs a detection-target signal that includes all of the input audio signals, and the signal-detection means detects the specified addition signal from the detection-target signal.
Moreover, the data-removal apparatus of this invention is presumed to remove the addition signal from the plurality of audio signals to which the addition signal was added. Here, a fourth operation means outputs a removal-target signal that includes all of the input audio signals, and a separation signal that includes at least two audio signals from the plurality of audio signals; and the signal-detection means detects the addition signal from the removal-target signal. Then, the signal-removal means removes the addition signal from the removal-target signal and outputs the result as a removal-completed signal; and a fifth operation means separates the plurality of audio signals from which the addition signal was removed based on the removal-completed signal and the separation signal.
Furthermore, the data-update apparatus of this invention is presumed to update a first addition signal that was added to the plurality of audio signals. Here, a sixth operation means outputs a detection-target signal that includes all of the input audio signals, and a separation signal that includes at least two of the audio signals; and the signal-detection means detects a first addition signal from detection-target signal. Furthermore, the signal-addition means adds a second addition signal to the detection-target signal based on the first addition signal that was detected by the signal-detection means, and together with outputting an addition-completed signal, a seventh operation means separates the audio signals to which the first and second additions signals were added based on the addition-completed signal and the separation signal.
Moreover, the signal-removal means removes the first addition signal, which was detected by the signal-detection means from the detection-target signal that was output by the sixth operation means, and outputs the result as a removal-completed signal; then the data-addition means adds a second addition signal to the removal-completed signal and outputs the result as an addition-completed signal, and the seventh operation means separates the audio signal to with the second addition means was added based on the addition-completed signal and the separation signal.
The data-addition apparatus, data-detection apparatus, data-removal apparatus, data-update apparatus and reproduction apparatus can also be realized using a computer. In this case, each process can be performed by operating a program on the computer.